Convalent conjugates of biologically-active compounds with amino acids and amino acid derivatives for targeting to physiologically-protected sites

ABSTRACT

This invention herein describes a method of facilitating the entry of drugs into cells and tissues at physiologically protected sites at pharmacokinetically useful levels and also a method of targeting drugs to physiologically protected sites in vivo. Also provided are drug conjugates with an amino acid or derivative thereof for facilitating such targeted drug delivery. The conjugates and methods of this invention provide an advance over other drug targeting methods known in the prior art, because the invention provides drug concentrations in such physiologically protected sites that can reach therapeutically-effective levels after administration of systemic levels much lower than are currently administered to achieve a therapeutic dose. This technology is appropriate for use with psychotropic, neurotropic, neurological, antibiotic, antibacterial, antimycotic, antiviral, antiproliferative or antineoplastic drugs, agents and conjugates, for rapid and efficient introduction of such agents across, e.g., the blood-brain barrier. Further, the invention provides means for retention and prolonged enzymatic release of such drugs, agents and conjugates comprising the conjugates of the invention, in the brain and central nervous system and other physiologically-protected sites.

This application claims priority to U.S. Ser. No. 09/993,976, filed Nov.5, 2001, now U.S. Pat. No. 7,045,543, granted May 16, 2006, which isincorporated by reference in its entirety.

BACKGROUND OF THE INVENTION

1. Field of the Invention

This invention is related to specific targeting of biologically-activecompounds to specific cells, tissues and organs in vivo. The inventionspecifically provides conjugates of biologically-active compounds andmethods of effecting the uptake and accumulation of biologically activecompounds into organs, tissues and cells, particularly atphysiologically protected sites, at pharmacokinetically useful levels.The conjugates of this invention permit drug concentrations to beachieved, especially at physiologically protected sites, at levels atwhich such compounds are therapeutically effective after administrationof systemic levels much lower than currently attainable otherwise. Thistechnology is appropriate for rapid and efficient introduction of avariety of biologically active compounds, particularly antibacterial,antibiotic, antiviral, antimycotic, antiproliferative and antineoplasticdrugs and agents, and neurotropic, psychotropic and anticonvulsant drugsand agents, to biologically protected sites, for example across theblood-brain barrier.

2. Background of the Invention

A major goal in the pharmacological arts has been the development ofmethods and compositions to facilitate the specific delivery oftherapeutic and other agents to the appropriate cells and tissues thatwould benefit from such treatment, and the avoidance of the generalphysiological effects of the inappropriate delivery of such agents toother cells or tissues of the body. One common example of the need forsuch specificity is in the field of neurologic agent therapy for thetreatment of diseases of the central nervous system, particularly thebrain, which is protected by a layer of endothelial cells and otherstructures collectively known as the blood-brain barrier. In thepharmacological and neurologic arts, it is well-recognized that theinability to deliver effective amounts of neurotropic, psychotropic andanticonvulsant drugs and agents across the blood-brain barrier severelylimits the therapeutic efficacy of such pharmaceutical compounds and canprevent treatment of neurologic disease. In addition, the use of eveneffective neurologic agents is further limited by systemic toxicityresulting from the high systemic concentrations that must beadministered to achieve a therapeutic concentration of such agents inthe brain, central nervous system and other neurological structures.Similar considerations apply in other organs and tissues in mammals thatare protected by such blood-related barriers, such as the testes.

Another example of the need for such specificity is for introducing oradministering antimicrobial, antiviral and antiproliferative andantineoplastic compounds, drugs or agents, intophysiologically-protected reservoirs in an animal such as the brain,central nervous system, eyes and testes. Avoiding general systemicside-effects is particularly important in administering antimicrobial,antiviral and antiproliferative and antineoplastic compounds, drugs oragents targeted to such physiologically-protected sites, since achievingclinically useful concentrations of said compounds at these sites hasfrequently required administration of high systemic dosages which areassociated with greater-than-acceptable levels of systemic toxicity.

It is desirable to increase the efficiency and specificity ofadministration of a therapeutic agent to the cells of the relevanttissues protected by physiological barriers (e.g., the blood-brainbarrier) in a variety of pathological states. Psychotropic, neurologicaland neurotropic agents and antimicrobial, antiviral andantiproliferative and antineoplastic compounds typically have systemiceffects, including renal and hepatotoxicity, hematopoietic suppression,teratogenic capacity, partitioning into breast milk and otherpleiotropic cytotoxic effects that damage or otherwise deleteriouslyimpact on uninvolved cells and tissues. Thus, an efficient deliverysystem which would enable the delivery of such drugs specifically tocells and tissues in such physiologically protected sites would increasethe efficacy of treatment and reduce the associated “side effects” ofsuch drug treatments, and also serve to reduce morbidity and mortalityassociated with clinical administration of such drugs. In addition,specific targeting of specific organs, tissues or cells wherein abiologically active compound preferentially accumulates in a specificorgan, tissue or cell and does not generally or systemically accumulatein organs, tissues or cells in a body is desirable.

An additional challenge in designing an appropriate drug delivery schemeis to include within the drug conjugate a functionality that couldeither accelerate or reduce the rate at which the drug is released uponarrival at the desired site. Such a functionality would be especiallyvaluable if it allowed differential rates of drug release, or specificrelease only at the appropriate drug target site comprising a specificorgan, tissue or cell in a body.

Drug Targeting

Numerous methods for enhancing the biological activity and thespecificity of drug action have been proposed or attempted (see, forexample, Kreeger, 1996, The Scientist, Sep. 16, 1996, p. 6). To date,however, efficient or specific drug delivery remains to be predictablyachieved.

U.S. Pat. No. 5,017,566, issued May 21, 1991 to Bodor discloses β- andγ-cyclodextrin derivatives comprising inclusion complexes of lipoidalforms of dihydropyridine redox targeting moieties.

U.S. Pat. No. 5,023,252, issued Jun. 11, 1991 to Hseih disclose the useof pharmaceutical compositions comprising a neurologically active drugand a compound for facilitating transport of said drug across theblood-brain barrier including a macrocyclic ester, diester, amide,diamide, amidine, diamidine, thioester, dithioester, thioamide, ketoneor lactone.

U.S. Pat. No. 5,024,998, issued Jun. 18, 1991 to Bodor disclosesparenteral solutions of aqueous-insoluble drugs with β- andγ-cyclodextrin derivatives.

U.S. Pat. No. 5,039,794, issued Aug. 13, 1991 to Wier et al. disclosethe use of a metastatic tumor-derived egress factor for facilitating thetransport of compounds across the blood-brain barrier.

U.S. Pat. No. 5,112,863, issued May 12, 1992 to Hashimoto et al.disclose the use of N-acyl amino acid derivatives as antipsychotic drugsfor delivery across the blood-brain barrier.

U.S. Pat. No. 5,124,146, issued Jun. 23, 1992 to Neuwelt disclose amethod for delivery of therapeutic agents across the blood-brain barrierat sites of increase permeability associated with brain lesions.

U.S. Pat. No. 5,149,794, issued Sep. 22, 1992 to Yatvin et al. discloseslipid conjugates with antineoplastic and antiviral drugs.

U.S. Pat. No. 5,153,179, issued Oct. 6, 1992 to Eibl discloses acylatedglycerol and derivatives for use in a medicament for improvedpenetration of cell membranes.

U.S. Pat. No. 5,177,064, issued Jan. 5, 1993 to Bodor discloses the useof lipoidal phosphonate derivatives of nucleoside antiviral agents fordelivery across the blood-brain barrier.

U.S. Pat. No. 5,223,263, issued Jun. 29, 1993 to Hostetler et al.discloses conjugates between antiviral nucleoside analogues and polarlipids, including phospholipids and ceramide.

U.S. Pat. No. 5,254,342, issued Oct. 19, 1993 to Shen et al. disclosereceptor-mediated transcytosis of the blood-brain barrier using thetransferrin receptor in combination with pharmaceutical compounds thatenhance or accelerate this process.

U.S. Pat. No. 5,256,641, issued Oct. 26, 1993 to Yatvin et al. discloseslipid conjugates with antigenic peptides.

U.S. Pat. No. 5,258,402, issued Nov. 2, 1993 to Maryanoff disclosestreatment of epilepsy with imidate derivatives of anticonvulsivesulfamate.

U.S. Pat. No. 5,270,312, issued Dec. 14, 1993 to Glase et al. disclosessubstituted piperazines as central nervous system agents.

U.S. Pat. No. 5,284,876, issued Feb. 8, 1994 to Shashoua et al.,disclose fatty acid conjugates of dopanergic drugs for tardivedyskinesia.

U.S. Pat. No. 5,389,623, issued Feb. 14, 1995 to Bodor discloses the useof lipoidal dihydropyridine derivatives of anti-inflammatory steroids orsteroid sex hormones for delivery across the blood-brain barrier.

U.S. Pat. No. 5,405,834, issued Apr. 11, 1995 to Bundgaard et al.discloses prodrug derivatives of thyrotropin releasing hormone.

U.S. Pat. No. 5,413,996, issued May 9, 1995 to Bodor discloseacyloxyalkyl phosphonate conjugates of neurologically-active drugs foranionic sequestration of such drugs in brain tissue.

U.S. Pat. No. 5,434,137, issued Jul. 18, 1995 to Black disclose methodsfor the selective opening of abnormal brain tissue capillaries usingbradykinin infused into the carotid artery.

U.S. Pat. No. 5,442,043, issued Aug. 15, 1995 to Fukuta et al. disclosea peptide conjugate between a peptide having a biological activity andincapable of crossing the blood-brain barrier and a peptide whichexhibits no biological activity and is capable of passing theblood-brain barrier by receptor-mediated endocytosis.

U.S. Pat. No. 5,466,683, issued Nov. 14, 1995 to Sterling et al.disclose water soluble analogues of the anticonvulsant Tegretol®(carbamazepine) for the treatment of epilepsy.

U.S. Pat. No. 5,484,809, issued Jan. 16, 1996 to Hostetler et al.discloses taxol and taxol derivatives conjugated to phospholipids.

U.S. Pat. No. 5,484,911, issued Jan. 16, 1996 to Hong et al. disclosenucleoside analogues conjugates to lipid moieties.

U.S. Pat. No. 5,512,671, issued Apr. 30, 1996 to Piantadosi et al.disclose nucleoside analogues conjugates to lipid moieties.

U.S. Pat. No. 5,525,727, issued Jun. 11, 1996 to Bodor disclosecompositions for differential uptake and retention in brain tissuecomprising a conjugate of a narcotic analgesic and agonists andantagonists thereof with a lipoidal form of dihydropyridine that forms aredox salt upon uptake across the blood-brain barrier that preventspartitioning back to the systemic circulation thereafter.

U.S. Pat. No. 5,543,389, issued Aug. 6, 1996 to Yatvin et al. disclosessalves and ointments for delivering antiproliferative compounds to skin.

U.S. Pat. No. 5,554,728, issued Sep. 10, 1996 to Basava et al. disclosestherapeutic peptides conjugated to lipid moieties.

U.S. Pat. No. 5,563,257, issued Oct. 8, 1998 to Zilch et al. disclosenucleoside analogues conjugates to ether lipid moieties.

U.S. Pat. No. 5,580,571, issued Dec. 3, 1996 to Hostetler et al.discloses nucleoside analogues conjugated to phospholipids.

U.S. Pat. No. 5,696,097, issued Dec. 9, 1997 to Matsuda et al. disclosenucleoside analogues conjugates to lipid moieties.

U.S. Pat. No. 5,744,461, issued Apr. 28, 1998 to Hostetler et al.disclose nucleoside analogues conjugated to phosphonoacetic acid lipidderivatives.

U.S. Pat. No. 5,744,592, issued Apr. 28, 1998 to Hostetler et al.discloses nucleoside analogues conjugated to phospholipids.

U.S. Pat. No. 5,756,116, issued May 26, 1998 to Hostetler et al.discloses nucleoside analogues.

U.S. Pat. No. 5,756,711, issued May 26, 1998 to Zilch et al. disclosenucleoside analogues conjugates to lipid moieties.

U.S. Pat. No. 5,827,819, issued Oct. 27, 1998 to Yatvin et al. discloseuse of polar lipid conjugates to facilitate delivery of neurologic drugsto tissues of the central nervous system across the blood brain barrier.

U.S. Pat. No. 5,827,831, issued Oct. 27, 1998 to Hostetler et al.discloses phospholipid-drug conjugates having enhanced gastrointestinalbioavailability.

International Patent Application Publication Number WO85/02342,published 6 Jun. 1985 for Max-Planck Institute discloses a drugcomposition comprising a glycerolipid or derivative thereof.

International Patent Application Publication Number WO89/02733,published Apr. 1989 to Vical discloses conjugates between antiviralnucleoside analogues and polar lipids, including phospholipids andceramide.

International Patent Application Publication Number WO89/11299,published 30 Nov. 1989 for State of Oregon disclose a chemical conjugateof an antibody with a an enzyme which is delivered specifically to abrain lesion site for activating a separately-administeredneurologically-active prodrug.

International Patent Application Publication Number WO91/04014,published 4 Apr. 1991 for Synergen, Inc. disclose methods for deliveringtherapeutic and diagnostic agents across the blood-brain barrier byencapsulating said drugs in liposomes targeted to brain tissue usingtransport-specific receptor ligands or antibodies.

International Patent Application Publication Number WO91/04745,published 18 Apr. 1991 for Athena Neurosciences, Inc. disclose transportacross the blood-brain barrier using cell adhesion molecules andfragments thereof to increase the permeability of tight junctions invascular endothelium.

International Patent Application Publication Number WO91/14438,published 3 Oct. 1991 for Columbia University disclose the use of amodified, chimeric monoclonal antibody for facilitating transport ofsubstances across the blood-brain barrier.

International Patent Application Publication Number WO94/01131,published 20 Jan. 1994 for Eukarion, Inc. disclose lipidized proteins,including antibodies. International Patent Application PublicationNumber WO94/03424, published 17 Feb. 1994 for Ishikura et al. disclosethe use of amino acid derivatives as drug conjugates for facilitatingtransport across the blood-brain barrier.

International Patent Application Publication Number WO94/06450,published 31 Mar. 1994 for the University of Florida disclose conjugatesof neurologically-active drugs with a dihydropyridine-type redoxtargeting moiety and comprising an amino acid linkage and an aliphaticresidue.

International Patent Application Publication Number WO94/02178,published 3 Feb. 1994 for the U.S. Government, Department of Health andHuman Services discloses antibody-targeted liposomes for delivery acrossthe blood-brain barrier.

International Patent Application Publication Number WO95/07092,published 16 Mar. 1995 for the University of Medicine and Dentistry ofNew Jersey disclose the use of drug-growth factor conjugates fordelivering drugs across the blood-brain barrier.

Intemational Patent Application Publication Number WO96/00537, published11 Jan. 1996 for Southern Research Institute disclose polymericmicrospheres as injectable drug-delivery vehicles for deliveringbioactive agents to sites within the central nervous system.

International Patent Application Publication Number WO96/04001,published 15 Feb. 1996 for Molecular/Structural Biotechnologies, Inc.disclose omega-3-fatty acid conjugates of neurologically-active drugsfor brain tissue delivery.

International Patent Application Publication Number WO96/22303,published 25 Jul. 1996 for the Commonwealth Scientific and IndustrialResearch Organization disclose fatty acid and glycerolipid conjugates ofneurologically-active drugs for brain tissue delivery.

International Patent Application Publication Number WO98/03204,published 29 Jan. 1998 for State of Oregon discloses salves andointments for delivering antiproliferative compounds to skin.

International Patent Application Publication Number WO98/17325,published 30 Apr. 1998 for Oregon Health Sciences University discloseslipid conjugates with neurologically-active drugs.

An additional challenge in designing an appropriate drug delivery schemeis to include within the drug conjugate a functionality that couldeither accelerate or reduce the rate at which the drug is released uponarrival at the desired site. Such a functionality would be especiallyvaluable if it allowed differential rates of drug release, or specificrelease only at the appropriate drug target site.

There remains a need in the art for an effective means for the specificdelivery of biologically-active compounds, particularly antibacterial,antibiotic, antiviral, antimycotic, antiproliferative and antineoplasticdrugs and agents, and also particularly neurotropic, psychotropic andanticonvulsant drugs and agents, and further particularly antineoplasticand anticancer drugs and agents, to physiologically restricted orprotected sites. Advantageous embodiments of such delivery means areformulated to efficiently deliver the biologically-active compound to aphysiologically-protected site, such as the brain or central nervoussystem, while minimizing hepatic and renal uptake of the agent orhematopoietic insult resulting therefrom.

SUMMARY OF THE INVENTION

The present invention is directed to an improved method for deliveringbiologically-active compounds, particularly drugs including preferablyantibacterial, antibiotic, antiviral, antimycotic, antiproliferative andantineoplastic drugs and agents, and neurotropic, psychotropic andanticonvulsant drugs and agents, to physiologically protected sites inan animal in vivo. This delivery system achieves specific delivery ofsuch biologically-active compounds through conjugating the compoundswith an amino acid or amino acid derivative that is specificallytransported into said physiologically-protected sites. This inventionhas the specific advantage of facilitating the entry of such compoundsinto cells and tissues protected by such physiological barriers as theblood-brain barrier via an amino acid or amino acid derivative that isspecifically transported into said physiologically-protected sites,achieving effective intracellular concentration of such compounds moreefficiently and with more specificity than conventional deliverysystems.

The invention provides compositions of matter comprising abiologically-active compound covalently linked to an amino acid or aminoacid derivative that is specifically transported into aphysiologically-protected site. Preferred embodiments also comprise aspacer molecule having two linker functional groups, wherein the spacerhas a first end and a second end and wherein the amino acid or aminoacid derivative is attached to the first end of the spacer through afirst linker functional group and the biologically-active compound isattached to the second end of the spacer through a second linkerfunctional group. In preferred embodiments, the biologically-activecompound is a drug, most preferably an antibacterial, antibiotic,antiviral, antimycotic, antiproliferative or antineoplastic drug oragent, or a neurotropic, psychotropic or anticonvulsant drug or agent.Preferred amino acid or amino acid derivatives include but are notlimited to hydroxytryptophan, serotonin, and most preferably melatonin.Pharmaceutical compositions comprising the drug/polar lipid conjugatesof the invention are also provided.

The invention also provides compositions of matter comprising abiologically-active compound covalently linked to an amino acid or aminoacid derivative via a spacer molecule wherein the spacer allows thebiologically-active compound to act without being released at anintracellular site. In these embodiments of the invention, the firstlinker functional group attached to the first end of the spacer ischaracterized as “strong” and the second linker functional groupattached to the second end of the spacer is characterized as “weak”,with reference to the propensity of the covalent bonds between each endof the spacer molecule to be broken.

In other embodiments of the compositions of matter of the invention, thespacer allows the facilitated hydrolytic release of thebiologically-active compound at an intracellular site. Other embodimentsof the spacer facilitate the enzymatic release of thebiologically-active compound at an intracellular site. In particularlypreferred embodiments, the spacer functional group is hydrolyzed by anenzymatic activity found in brain tissue, including neuronal, glial andother brain cell types, preferably an esterase and most preferably anesterase having a differential expression and activity profile in theappropriate target cell type. In additional preferred embodiments,specific release of biologically-active compounds is achieved byenzymatic or chemical release of the biologically-active compound byextracellular cleavage of a cleavable linker moiety via an enzymaticactivity specific for brain tissue, with resulting specific uptake ofthe released antibacterial, antibiotic, antiviral, antimycotic,antiproliferative or antineoplastic drug or agent, or a neurotropic,psychotropic or anticonvulsant drug or agent by the appropriate cell insaid tissue.

In another embodiment of this aspect of the invention, the spacermolecule is a peptide of formula (amino acid)n, wherein n is an integerbetween 2 and 25, preferably wherein the peptide comprises a polymer ofone or more amino acids.

In other embodiments of the compositions of matter of the invention, thebiologically-active compound of the invention has a first functionallinker group, and an amino acid or amino acid derivative that isspecifically transported into a physiologically-protected site having asecond functional linker group, and the compound is covalently linkeddirectly to the amino acid or amino acid derivative by a chemical bondbetween the first and second functional linker groups. In preferredembodiments, each of the first and second functional linker groups is ahydroxyl group, a primary or secondary amino group, a phosphate group orsubstituted derivatives thereof or a carboxylic acid group.

In another aspect of the invention is provided compositions of mattercomprising a drug, most preferably an antibacterial, antibiotic,antiviral, antimycotic, antiproliferative or antineoplastic drug oragent, or a neurotropic, psychotropic or anticonvulsant drug or agent,covalently linked to an amino acid or amino acid derivative that isspecifically transported into a physiologically-protected site.Preferred embodiments also comprise a spacer molecule having two linkerfunctional groups, wherein the spacer has a first end and a second endand wherein the amino acid or amino acid derivative is attached to thefirst end of the spacer through a first linker functional group and thedrug is attached to the second end of the spacer through a second linkerfunctional group. Preferred embodiments of the invention are providedwherein the drug is an antibacterial, antibiotic, antiviral,antimycotic, antiproliferative or antineoplastic drug or agent, or aneurotropic, psychotropic or anticonvulsant drug or agent. Preferredamino acid or amino acid derivatives include but are not limited tohydroxytryptophan, serotonin, and most preferably melatonin.Pharmaceutical compositions comprising the conjugates of the inventionare also provided.

The invention also provides compositions of matter comprisingantibacterial, antibiotic, antiviral, antimycotic, antiproliferative orantineoplastic drug or agent, or a neurotropic, psychotropic oranticonvulsant drug or agent, covalently linked to an amino acid oramino acid derivative via a spacer molecule, wherein the spacer allowsthe drug to act without being released at an intracellular site. Inthese embodiments of the invention, the first linker functional groupattached to the first end of the spacer is characterized as “strong” andthe second linker functional group attached to the second end of thespacer is characterized as “weak”, with reference to the propensity ofthe covalent bonds between each end of the spacer molecule to be broken.

In other embodiments of the compositions of matter of the invention, thespacer allows the facilitated hydrolytic release of antibacterial,antibiotic, antiviral, antimycotic, antiproliferative or antineoplasticdrug or agent, or a neurotropic, psychotropic or anticonvulsant drug oragent at an intracellular site. Other embodiments of the spacerfacilitate the enzymatic release of the antibacterial, antibiotic,antiviral, antimycotic, antiproliferative or antineoplastic drug oragent, or a neurotropic, psychotropic or anticonvulsant drug or agent ofthe invention at an intracellular site. In particularly preferredembodiments, the spacer functional group is hydrolyzed by an enzymaticactivity found in a physiologically-protected site, such as the brainand central nervous system and more particularly including neuronal,glial and other brain cell types, wherein said enzymatic activity ispreferably an esterase and most preferably an esterase having adifferential expression and activity profile in different tissue celltypes. In additional preferred embodiments, specific release of theantibacterial, antibiotic, antiviral, antimycotic, antiproliferative orantineoplastic drug or agent, or a neurotropic, psychotropic oranticonvulsant drug or agent of the invention is achieved by enzymaticor chemical release of these drugs by extracellular cleavage of acleavable linker moiety via an enzymatic activity specific for, forexample, brain tissue, followed by specific uptake of the releasedantibacterial, antibiotic, antiviral, antimycotic, antiproliferative orantineoplastic drug or agent, or a neurotropic, psychotropic oranticonvulsant drug or agent by the appropriate cell in said tissue.

In another embodiment of this aspect of the invention, the spacermolecule is a peptide of formula (amino acid)n, wherein n is an integerbetween 2 and 25, preferably wherein the peptide comprises a polymer ofone or more amino acids.

In still further embodiments of the compositions of matter of theinvention are provided antibacterial, antibiotic, antiviral,antimycotic, antiproliferative or antineoplastic drug or agent, or aneurotropic, psychotropic or anticonvulsant drug or agent having a firstfunctional linker group, and an amino acid or amino acid derivativehaving a second functional linker group, wherein the drug is covalentlylinked directly to the polar lipid carrier by a chemical bond betweenthe first and second functional linker groups. In preferred embodiments,each of the first and second functional linker groups is a hydroxylgroup, a primary or secondary amino group, a phosphate group orsubstituted derivatives thereof or a carboxylic acid group. Preferredamino acid or amino acid derivatives include but are not limited tohydroxytryptophan, serotonin, and most preferably melatonin.Pharmaceutical compositions comprising the conjugates of the inventionare also provided.

As disclosed herein, the invention comprehends conjugates wherein theamino acid or amino acid derivative is specifically and selectivelytransported across certain physiological barriers to protected tissuesites, thereby facilitating delivery of drugs and other pharmaceuticalagents to such physiologically restricted or protected sites. Inembodiments comprising a spacer moiety, the spacer component of theconjugates of the invention will preferably act to specifically releasethe drug from the amino acid or derivative at the target site; preventthe non-specific release from the drug from the amino acid or derivativein the systemic circulation or in hepatic, renal or other inappropriatecells, tissue or organs; target the conjugate to a specific cell or celltype within the protected tissue; prevent interaction and/or uptake ofthe drug by hematopoietic, ocular, hepatic or renal tissues; or performother functions to maximize the effectiveness of the drug.

This type of conjugate has numerous advantages. The conjugates of theinvention provide delivery of a variety of antibacterial, antibiotic,antiviral, antimycotic, antiproliferative or antineoplastic drug oragent, or a neurotropic, psychotropic or anticonvulsant drug or agent tophysiologically restricted or protected sites in vivo at concentrationsand pharmacokinetic rates not heretofore attainable. A benefit of thisadvantage is the achievement of therapeutic indices of agents in suchprotected sites whereby the agent is useful for achieving a desiredtherapeutic goal. Another benefit is decreased hepatic toxicity,hematopoietic suppression (such as thrombocytopenia, leukopenia,aplastic anemia, leukocytosis, eosinophilia, pancytopenia,agranulocytosis), reduced systemic metabolism, degradation and toxicity,reduced hepatic clearance, reduced systemic adverse drug interactions,and generally reduced side effects due to the achievement of a lower,therapeutically-effective dose as the result of surmounting thephysiological barrier. These biological effects can also result insimplified dosage schedules, particularly for drugs with short systemichalf-lives.

In particular, felicitous design of the psychotropic,neurotropic/neurological drug/spacer/amino acid conjugate can provide anin vivo reservoir of time-dependent drug release in the physiologicallyprotected tissue, resulting in specific delivery of therapeutic amountsto such tissues using a reduced dosage regime to minimize non-specific,systemic and deleterious side effects. In such formulations, the amountand activity of the antibacterial, antibiotic, antiviral, antimycotic,antiproliferative or antineoplastic drug or agent, or a neurotropic,psychotropic or anticonvulsant drug or agent can be modulated by releasevia cleavage, preferably hydrolytic cleavage, of the spacer moiety, mostpreferably by an enzymatic activity in the protected tissue (e.g.,brain) that has a differential pattern of expression or activity indifferent cell types in said tissue. The conjugates of the invention canalso be combined with other drug delivery approaches to further increasespecificity and to take advantage of useful advances in the art.

Specific preferred embodiments of the present invention will becomeevident from the following more detailed description of certainpreferred embodiments and the claims.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 illustrates two conjugates of the invention between leva-dopa andmelatonin. These conjugates are cleaved by esterases expressed intissues in biologically-protected sites.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

The present invention provides compositions of matter and methods forfacilitating the entry into cells of biologically-active compounds. Forthe purposes of this invention, the term “biologically-active compound”is intended to encompass all naturally-occurring or synthetic compoundscapable of eliciting a biological response or having an effect, eitherbeneficial or cytotoxic, on biological systems, particularly cells andcellular organelles. These compounds are intended to include but are notlimited to all varieties of drugs, particularly antibacterial,antibiotic, antiviral, antimycotic, antiproliferative and antineoplasticdrugs and agents, and neurotropic, psychotropic and anticonvulsant drugsor agents.

As used herein the terms “psychotropic, neurotropic andneurologically-acting drugs and agents” are intended to include anydrug, agent or compound having a neurological, neurotropic, orpsychotropic effect in an animal, preferably a human. These terms areintended to encompass anti-inflammatory agents, corticosteroids,sedatives, tranquilizers, narcotics, analgesics, anesthetics,anticonvulsive and antispasmodic agents, antiparkinsonian drugs,alkaloids, catecholamines, including dopamine analogues and derivatives,muscarinic receptor agonists and antagonists, cholinergic receptoragonists and antagonists, calcium channel blockers, γ-aminobutyric acid(GABA) receptor agonists, antagonists, and uptake inhibitors andenhancers; phenothiazines, thioxanthemes and related compounds;clozapine, haldoperidol, loxapine (Loxitane®), benzodiazapeneantidepressants of the norepinephrine reuptake inhibitor type; monoamineoxidase inhibitors; antidepressants and antimanic agents, antioxidantssuch as carotenes, glutathione, N-acetylcysteine or other molecules thatmitigate the effects of reactive oxygen species for the treatment ofAlzheimer's disease, Parkinson's disease, or other neurodegenerativeconditions such as ataxia telangiectasia and amyelolaterosclerosis(ALS); neuroregenerative agents; and agents for the treatment ofischemia and other vascular diseases of the central nervous system.Appropriate formulations and pharmaceutical compositions of theneurotropic/neurological/psychotropic drug/amino acid or derivativeconjugates of the invention will be apparent and within the skill of oneof ordinary skill in this art to advantageously prepare in view of theinstant disclosure.

As used herein the terms “antibiotic, antibacterial, antimycotic,antiviral, antiproliferative or antineoplastic drugs and agents” areintended to include any drug, agent or compound having an antibiotic,antibacterial, antimycotic, antiviral, antiproliferative orantineoplastic effect in an animal, preferably a human. In particular,the term “antimicrobial drug” will be understood to encompass saidantibiotic, antibacterial, antimycotic, and antiviral compounds, as wellas other compounds that have an antimicrobial effect (such asanti-plasmodial drugs).

For the purposes of this invention, the term “antimicrobial drug” isintended to encompass any pharmacological agent effective in inhibiting,attenuating, combating or overcoming infection of mammalian cells by amicrobial pathogen in vivo or in vitro. Antimicrobial drugs as providedas components of the antimicrobial agents of the invention include butare not limited to penicillin and drugs of the penicillin family ofantimicrobial drugs, including but not limited to penicillin-G,penicillin-V, phenethicillin, ampicillin, amoxacillin, cyclacillin,bacampicillin, hetacillin, cloxacillin, dicloxacillin, methicillin,nafcillin, oxacillin, azlocillin, carbenicillin, mezlocillin,piperacillin, ticaricillin, and imipenim; cephalosporin and drugs of thecephalosporin family, including but not limited to cefadroxil,cefazolin, caphalexin, cephalothin, cephapirin, cephradine, cefaclor,cefamandole, cefonicid, cefoxin, cefuroxime, ceforanide, cefotetan,cefinetazole, cefoperazone, cefotaxime, ceftizoxime, ceftizone,moxalactam, ceftazidime, and cefixime; aminoglycoside drugs and drugs ofthe aminoglycoside family, including but not limited to streptomycin,neomycin, kanamycin, gentamycin, tobramycin, amikacin, and netilmicin;macrolide and drugs of the macrolide family, exemplified byazithromycin, clarithromycin, roxithromycin, erythromycin, lincomycin,and clindamycin; tetracycline and drugs of the tetracycline family, forexample, tetracycline, oxytetracycline, democlocyclin, methacyclin,doxycyclin, and minocyclin; quinoline and quinoline-like drugs, such as,for example, naladixic acid, cinoxacin, norfloxacin, ciprofloxacin,ofloxicin, enoxacin, and pefloxacin; antimicrobial peptides, includingbut not limited to polymixin B, colistin, and bacitracin, as well asother antimicrobial peptides such as defensins (Lehrer et al., 1991,Cell 64: 229-230), magainins (Zasloff, 1987, Proc. Natl. Acad. Sci. USA84: 5449-5453), cecropins (Lee et al., 1989, Proc. Natl. Acad. Sci. USA86: 9159-9162 and Boman et al., 1990, Eur. J. Biochem. 201: 23-31), andothers, provided as naturally-occurring, chemically synthesized in vitroor produced as the result of engineering to make such peptides resistantto the action of pathogen-specific proteases and other deactivatingenzymes; other antimicrobial drugs, including chloramphenicol,vancomycin, rifampicin, metronidazole, ethambutol, pyrazinamide,sulfonamides, isoniazid, and erythromycin.

Antiviral drugs, including but not limited to reverse transcriptaseinhibitors, protease inhibitors, antiherpetics such as acyclovir andgancyclovir, azidothymidine, cytidine arabinoside, ribavirin,amantadine, iododeoxyuridine, foscamet, trifluoridine, methizazone,vidarabine and levanisole are also encompassed by this definition andare expressly included therein.

Antimycotic drugs provided by the invention and comprising thepharmaceutical compositions thereof include but are not limited toclotrimazole, nystatin, econazole and myconixole, ketoconazole,grisefulvin, ciclopixox, naftitine and other imidizole antimycotics.

Antiproliferative and antineoplastic agents provided by the inventionand comprising the pharmaceutical compositions thereof include but arenot limited to methotrexate, doxarubicin, daunarubicin,epipodophyllotoxins, 5-fluorouracil, tamoxifen, actinomycin D,vinblastine, vincristine, colchicine and taxol.

The invention also provides antibiotic drugs and agents wherein anantimicrobial agent is a toxin capable of specific cytotoxicity againstthe microbe, its host cell or both. The term “toxin” is intended toencompass any pharmacological agent capable of such toxicity, includingfor example ricin from jack bean, diphtheria toxin, and othernaturally-occurring and man-made toxins.

The conjugates of the invention comprise the biologically-activecompounds of the invention covalently linked to an amino acid or aminoacid derivative that is specifically transported into aphysiologically-protected site. Such compounds include but are notlimited to 5-hydroxytryptophan, serotonin, and most preferablymelatonin. The amino acids and derivative thereof encompassed by thisdefinition include any amino acid, naturally-occurring or synthetic, andany derivative of an amino acid, including primary, secondary andtertiary amines, carboxylic acids, esters, amides, aldehydes, alcohols,ethers, and thiols, provided that any such derivative is preferentiallypartitioned into a physiologically protected site in vivo, including butnot limited to eye, spleen, lung, testes and the central nervous system,most preferably the brain.

Appropriate formulations and pharmaceutical compositions of theconjugates of the invention comprising antibacterial, antibiotic,antiviral, antimycotic, antiproliferative and antineoplastic drugs oragents, or neurotropic, psychotropic or anticonvulsant drugs or agentswill be apparent and within the skill of one of ordinary skill in thisart to advantageously prepare in view of the instant disclosure. Inpreferred embodiments, said pharmaceutical compositions are provided fortopical application, comprising appropriately chosen salves, ointmentsand emollients. In particularly preferred embodiments, said topicalapplication is specifically adapted for administration to oculartissues, comprising electrolytically balanced solutions for topical anddirect administration to vertebrate, preferably mammalian and mostpreferably human eyes. In alternative formulations, the pharmaceuticalcomposition comprises complexes formed for example with serum albumin,polyvinylpyrrolidone and other pharmaceutically acceptable carriers andexcipients for parenteral administration, including but not limited tointravenous, intramuscular, and subcutaneous routes of administration.In yet alternative embodiments, the pharmaceutical compositions of theinvention are provided to be orally bioavailable by administration intablets, capsules, elixirs, gums, and other formulations comprisingexcipients adapted for transit of the conjugates of the inventionthrough the gastrointestinal tract. Oral and parenteral routes ofadministration are preferred.

In preferred embodiments, the conjugates are provided wherein thebiologically active compound is in a form having reduced, inhibited, oressentially no biological activity and wherein this form of the compoundis capable of being converted by chemical or enzymatic means, mostpreferably in vivo, into a form having a desired biological activity;when the biologically active compound is a drug, this form of the drugis commonly termed a “prodrug.” Embodiments of such prodrugs useful inthe present invention include prodrugs that can be converted by chemicalor enzymatic means in a targeted organ, tissue or cell in an animal. Inpreferred embodiments, said prodrugs are converted into a form having adesired biological activity in an organ or tissue extracellularly, i.e.within the physical and anatomically-recognized province of the organ ortissue but not within any particular cell in the organ or tissue. Insuch embodiments, the activated prodrug is then capable of having thedesired biological activity without entry into any particular cellcomprising said organ or tissue. In alternative embodiments, theactivated prodrug is then capable of entering a cell comprising saidorgan or tissue and having the desired biological activity thereof. Inadditional preferred embodiments, the prodrug is only converted into theactive form after entry into a particular cell or cell type comprisingsaid organ or tissue.

As used herein, the terms “chemical or enzymatic means” is intended toencompass chemical conditions (including but not limited to salt orother electrolyte concentration, metabolite concentration, pH,osmolality, osmolarity, dielectric constant, temperature, pressure, orchemical catalyst concentration) or presence of enzymatic activity(including but not limited to esterases, amidases, peptidases,nucleases, peroxidases, lipases, or redox proteins) in an organ, tissueor cell, most preferably in a physiologically-protected site in ananimal, most preferably a human. It will be understood that the choiceof spacer moiety comprising any particular embodiment of thepharmaceutical compositions or compositions of matter of the invention,and particularly the choice of said linker functional groups comprisingsaid spacer moieties, is chosen to match the chemical or enzymatic meanspresent in the organ, tissue or cell targeted by said composition.

The compositions of matter and pharmaceutical compositions of theinvention may further comprise a spacer moiety comprising a first endand a second end, each end of the spacer having a functional linkinggroup. For the purposes of this invention, the term “spacer” or “spacermoiety” is intended to encompass any chemical entity that links abiologically-active compound and an amino acid or derivative thereofaccording to the invention. Such spacer moieties may be designed topromote or effect the delivery to or accumulation at specific organs,tissues or cells, or to promote, influence, modulate or regulate therelease of the biologically-active compound at the desired target site.Such spacers may facilitate enzymatic release at specific organs,tissues and cell, preferably at extracellular sites therein; morepreferably, said spacers inhibit enzymatic, hydrolytic or other releasesystemically in an animal. Spacer groups, as described herein, include,but are not limited to aminohexanoic acid, adipic acid, and otherbifunctional organic acids; peptides including homopolymers such aspolyglycine; substituted fatty acids; carbohydrate moieties includingmono-, di- and other saccharides; oligonucleotides; polyamides,polyethylenes, and short functionalized polymers having a carbonbackbone which is from one to about twelve carbon molecules in length.Particularly preferred embodiments of such spacer moieties comprisepeptides of formula (amino acid)n, wherein n is an integer between 2 and25 and the peptide is a polymer of one or more amino acids.

The term “linker functional group” is defined herein as any functionalgroup for covalently binding the amino acid or derivative thereof orbiologically-active agent to the spacer group. These groups can bedesignated either “weak” or “strong” based on the stability of thecovalent bond that the linker functional group will form between thespacer and either the amino acid or derivative thereof or thebiologically-active compound. The weak functionalities include, but arenot limited to phosphoramide, phosphoester, carbonate, amide,carboxyl-phosphoryl anhydride, thioester and most preferably ester. Thestrong functionalities include, but are not limited to ether, thioether,amine, amide and most preferably ester. The use of a strong linkerfunctional group between the spacer group and the biologically-activecompound will tend to decrease the rate at which the compound will bereleased at the target site, whereas the use of a weak linker functionalgroup between the spacer group and the compound may act to increase therelease rate of the compound at the target site. Enzymatic release is,of course, also possible, but such enzyme-mediated modes of release willnot necessarily be correlated with bond strength in such embodiments ofthe invention. Spacer moieties comprising enzyme active site recognitiongroups, such as spacer groups comprising peptides having proteolyticcleavage sites therein, are envisioned as being within the scope of thepresent invention. Specifically, such specifically-cleavable peptidesare preferably prepared so as to be recognized by enzymes present inparticular organs or tissues such as brain and other physiologicallyrestricted or protected sites in vivo, so that the drug ispreferentially liberated from the polar lipid conjugate at appropriatedrug delivery sites. An illustrative example of such aspecifically-cleavable peptide is a portion of the proopiomelanocortinfamily of peptides, which are cleaved in mammalian brain tissue torelease a variety of peptides hormones and effector molecules, such asthe enkephalins. Those of ordinary skill in the art will recognize otherbeneficial and advantageous specifically-cleavable peptides. The linkerfunctional groups are selected to inhibit or prevent cleavage of thecovalent linkage between the spacer and the biologically activecompound, or between the spacer and the polar lipid carrier, at a siteother than the specific site to which the conjugate is targeted.

The conjugates of the invention are preferably provided comprised ofspacer moieties that impart differential release properties on theconjugates related to differential expression or activity of enzymaticactivities in physiologically restricted or protected sites incomparison with such activities in systemic circulation or ininappropriate targets, such as hepatic, renal or hematopoietic tissues.Differential release is also provided in certain embodiments in specificcell types comprising such physiologically protected tissues.

In particularly preferred embodiments of the present invention areprovided conjugates comprising neurotropic, psychotropic andanticonvulsant drugs or agents for specific delivery to brain tissue forthe alleviation or amelioration of pathological disease states in thebrain. Thus, the present invention provides methods and compositions ofmatter for facilitating the transit of such conjugates of antibacterial,antibiotic, antiviral, antimycotic, antiproliferative and antineoplasticdrugs and agents, and neurotropic, psychotropic and anticonvulsant drugsor agents across the blood-brain barrier and into targeted regions ofthe brain, for the treatment of animal, preferably human, diseases andpathological conditions. Among the most common such diseases andconditions are Alzheimer's disease, Parkinson's disease, epilepsy andother seizure disorders (such as petit mal, grand mal, tonic-clonicseizure disorder, parietal complex seizure, and psychomotor seizures),migraine, neurodegenerative conditions such as ataxia telangiectasia andALS, Lennox-Gastaut syndrome, neuropathy such as trigeminal neuralgia,diabetic neuropathy, shingles, and psychological disorders, includingbipolar disorder, explosive aggression, depression and agitationassociated with elderly dementia.

The invention provides conjugates comprising psychotropic, neurotropicand neurological drugs, agents and compounds including but not limitedto L-dopa, hydroxytryptamine and metabolites thereof; amantadine,benztropine, bromocryptine, diphenhydramine, levadopa (a particularlypreferred embodiment) and combinations thereof (e.g., with carbidopa asprovided as Sinemet®); pergolid, trihexphenidyl, ethosuximide, valproicacid, carbamazepine (e.g., Tegretol®) and, in a particularly preferredembodiment, the 10- or 11-hydroxy analogues of carbamazepine; primidone,gabapentin in a particularly preferred embodiment; lamotrigine in aparticularly preferred embodiment; felbamate, paramethadione andtrimethadione; phenothiazines, thioxanthemes and related compounds;clozapine, haldoperidol, loxapine (Loxitane®), benzodiazapeneantidepressants of the norepinephrine reuptake inhibitor type; monoamineoxidase inhibitors, and antioxidants such as carotenes, glutathione andN-acetylcysteine.

The invention provides conjugates comprising antibiotic, antibacterial,antimycotic, antiviral, antiproliferative or antineoplastic drugs,agents and compounds including but not limited to methotrexate,azidothymidine, dideoxyinosine, dideoxycytosine, acyclovir, organcyclovir.

The invention specifically provides methods for preparing andadministering such psychotropic, neurotropic, neurological, antibiotic,antibacterial, antimycotic, antiviral, antiproliferative orantineoplastic drugs, agent and compounds for use in treatingpathological conditions in vivo.

The invention also provides embodiments of the conjugates disclosedherein as pharmaceutical compositions. The pharmaceutical compositionsof the present invention can be manufactured in a manner that is itselfknown, e.g., by means of a conventional mixing, dissolving, granulating,dragee-making, levigating, emulsifying, encapsulating, entrapping orlyophilizing processes.

Pharmaceutical compositions for use in accordance with the presentinvention thus can be formulated in conventional manner using one ormore physiologically acceptable carriers comprising excipients andauxiliaries that facilitate processing of the active conjugates intopreparations that can be used pharmaceutically. Proper formulation isdependent upon the route of administration chosen.

Non-toxic pharmaceutical salts include salts of acids such ashydrochloric, phosphoric, hydrobromic, sulfuric, sulfinic, formic,toluenesulfonic, methanesulfonic, nitic, benzoic, citric, tartaric,maleic, hydroiodic, alkanoic such as acetic, HOOC—(CH₂)_(n)—CH₃ where nis 0-4, and the like. Non-toxic pharmaceutical base addition saltsinclude salts of bases such as sodium, potassium, calcium, ammonium, andthe like. Those skilled in the art will recognize a wide variety ofnon-toxic pharmaceutically acceptable addition salts.

For injection, the conjugates of the invention can be formulated inappropriate aqueous solutions, such as physiologically compatiblebuffers such as Hanks' solution, Ringer's solution, or physiologicalsaline buffer. For transmucosal and transcutaneous administration,penetrants appropriate to the barrier to be permeated are used in theformulation. Such penetrants are generally known in the art.

For oral administration, the conjugates can be formulated readily bycombining the active conjugates with pharmaceutically acceptablecarriers well known in the art. Such carriers enable the conjugates ofthe invention to be formulated as tablets, pills, dragees, capsules,liquids, gels, syrups, slurries, suspensions and the like, for oralingestion by a patient to be treated. Pharmaceutical preparations fororal use can be obtained with solid excipient, optionally grinding aresulting mixture, and processing the mixture of granules, after addingsuitable auxiliaries, if desired, to obtain tablets or dragee cores.Suitable excipients are, in particular, fillers such as sugars,including lactose, sucrose, mannitol, or sorbitol; cellulosepreparations such as, for example, maize starch, wheat starch, ricestarch, potato starch, gelatin, gum tragacanth, methyl cellulose,hydroxypropylmethylcellulose, sodium carboxymethylcellulose, and/orpolyvinylpyrrolidone (PVP). If desired, disintegrating agents can beadded, such as the cross-linked polyvinyl pyrrolidone, agar, or alginicacid or a salt thereof such as sodium alginate.

Dragee cores are provided with suitable coatings. For this purpose,concentrated sugar solutions can be used, which can optionally containgum arabic, talc, polyvinyl pyrrolidone, carbopol gel, polyethyleneglycol, and/or titanium dioxide, lacquer solutions, and suitable organicsolvents or solvent mixtures. Dyestuffs or pigments can be added to thetablets or dragee coatings for identification or to characterizedifferent combinations of active compound doses.

Pharmaceutical preparations that can be used orally include push-fitcapsules made of gelatin, as well as soft, sealed capsules made ofgelatin and a plasticizer, such as glycerol or sorbitol. The push-fitcapsules can contain the active ingredients in admixture with fillersuch as lactose, binders such as starches, and/or lubricants such astalc or magnesium stearate and, optionally, stabilizers. In softcapsules, the active conjugates can be dissolved or suspended insuitable liquids, such as fatty oils, liquid paraffin, or liquidpolyethylene glycols. In addition, stabilizers can be added. Allformulations for oral administration should be in dosages suitable forsuch administration. For buccal administration, the compositions cantake the form of tablets or lozenges formulated in conventional manner.

For administration by inhalation, the conjugates for use according tothe present invention are conveniently delivered in the form of anaerosol spray presentation from pressurized packs or a nebuliser, withthe use of a suitable propellant, e.g., dichlorodifluoromethane,trichlorofluoromethane, dichlorotetrafluoroethane, carbon dioxide orother suitable gas. In the case of a pressurized aerosol the dosage unitcan be determined by providing a valve to deliver a metered amount.Capsules and cartridges of e.g., gelatin for use in an inhaler orinsufflator can be formulated containing a powder mix of the compoundand a suitable powder base such as lactose or starch.

The conjugates can be formulated for parenteral administration byinjection, e.g., by bolus injection or continuous infusion. Formulationsfor injection can be presented in unit dosage form, e.g., in ampoules orin multi-dose containers, with an added preservative. The compositionscan take such forms as suspensions, solutions or emulsions in oily oraqueous vehicles, and can contain formulatory agents such as suspending,stabilizing and/or dispersing agents.

Pharmaceutical formulations for parenteral administration includeaqueous solutions of the active conjugates in water-soluble form.Additionally, suspensions of the active conjugates can be prepared asappropriate oily injection suspensions. Suitable lipophilic solvents orvehicles include fatty oils such as sesame oil, or synthetic fatty acidesters, such as ethyl oleate or triglycerides, or liposomes. Aqueousinjection suspensions can contain substances that increase the viscosityof the suspension, such as sodium carboxymethyl cellulose, sorbitol, ordextran. Optionally, the suspension can also contain suitablestabilizers or agents that increase the solubility of the conjugates toallow for the preparation of highly concentrated solutions.Alternatively, the active ingredient can be in powder form forconstitution with a suitable vehicle, e.g., sterile pyrogen-free water,before use. The conjugates can also be formulated in rectal compositionssuch as suppositories or retention enemas, e.g., containing conventionalsuppository bases such as cocoa butter or other glycerides.

In addition to the formulations described previously, the conjugates canalso be formulated as a depot preparation. Such long acting formulationscan be administered by implantation (for example subcutaneously orintramuscularly) or by intramuscular injection. Thus, for example, theconjugates can be formulated with suitable polymeric or hydrophobicmaterials (for example as an emulsion in an acceptable oil) or ionexchange resins, or as sparingly soluble derivatives, for example, as asparingly soluble salt.

A pharmaceutical carrier for the hydrophobic conjugates of the inventionis a cosolvent system comprising benzyl alcohol, a nonpolar surfactant,a water-miscible organic polymer, and an aqueous phase. The cosolventsystem can be the VPD co-solvent system. VPD is a solution of 3% w/vbenzyl alcohol, 8% w/v of the nonpolar surfactant polysorbate 80, and65% w/v polyethylene glycol 300, made up to volume in absolute ethanol.The VPD co-solvent system (VPD:5W) consists of VPD diluted 1:1 with a 5%dextrose in water solution. This co-solvent system dissolves hydrophobicconjugates well, and itself produces low toxicity upon systemicadministration. Naturally, the proportions of a co-solvent system can bevaried considerably without destroying its solubility and toxicitycharacteristics. Furthermore, the identity of the co-solvent componentscan be varied: for example, other low-toxicity nonpolar surfactants canbe used instead of polysorbate 80; the fraction size of polyethyleneglycol can be varied; other biocompatible polymers can replacepolyethylene glycol, e.g. polyvinyl pyrrolidone; and other sugars orpolysaccharides can substitute for dextrose.

Alternatively, other delivery systems for hydrophobic pharmaceuticalconjugates can be employed. Liposomes and emulsions are well knownexamples of delivery vehicles or carriers for hydrophobic drugs. Certainorganic solvents such as dimethylsulfoxide also can be employed,although usually at the cost of greater toxicity. Additionally, theconjugates can be delivered using a sustained-release system, such assemipermeable matrices of solid hydrophobic polymers containing thetherapeutic agent. Various sustained-release materials have beenestablished and are well known by those skilled in the art.Sustained-release capsules can, depending on their chemical nature,release the conjugates for a few weeks up to over 100 days. Depending onthe chemical nature and the biological stability of the therapeuticreagent, additional strategies for protein and nucleic acidstabilization can be employed.

The pharmaceutical compositions also can comprise suitable solid or gelphase carriers or excipients. Examples of such carriers or excipientsinclude but are not limited to calcium carbonate, calcium phosphate,various sugars, starches, cellulose derivatives, gelatin, and polymerssuch as polyethylene glycols.

The conjugates of the invention can be provided as salts withpharmaceutically compatible counterions. Pharmaceutically compatiblesalts can be formed with many acids, including but not limited tohydrochloric, sulfuric, acetic, lactic, tartaric, malic, succinic,phosphoric, hydrobromic, sulfinic, formic, toluenesulfonic,methanesulfonic, nitic, benzoic, citric, tartaric, maleic, hydroiodic,alkanoic such as acetic, HOOC—(CH₂)_(n)—CH₃ where n is 0-4, and thelike. Salts tend to be more soluble in aqueous or other protonicsolvents that are the corresponding free base forms. Non-toxicpharmaceutical base addition salts include salts of bases such assodium, potassium, calcium, ammonium, and the like. Those skilled in theart will recognize a wide variety of non-toxic pharmaceuticallyacceptable addition salts.

Pharmaceutical compositions of the conjugates of the present inventioncan be formulated and administered through a variety of means, includingsystemic, localized, or topical administration. Techniques forformulation and administration can be found in “Remington'sPharmaceutical Sciences,” Mack Publishing Co., Easton, Pa. The mode ofadministration can be selected to maximize delivery to a desired targetsite in the body. Suitable routes of administration can, for example,include oral, rectal, transmucosal, transcutaneous, or intestinaladministration; parenteral delivery, including intramuscular,subcutaneous, intramedullary injections, as well as intrathecal, directintraventricular, intravenous, intraperitoneal, intranasal, orintraocular injections.

Alternatively, one can administer the conjugates in a local rather thansystemic manner, for example, via injection of the compound directlyinto a specific tissue, often in a depot or sustained releaseformulation.

Pharmaceutical compositions suitable for use in the present inventioninclude compositions wherein the active ingredients are contained in aneffective amount to achieve its intended purpose. More specifically, atherapeutically effective amount means an amount effective to preventdevelopment of or to alleviate the existing symptoms of the subjectbeing treated. Determination of the effective amounts is well within thecapability of those skilled in the art, especially in light of thedetailed disclosure provided herein.

For any conjugate species used in the method of the invention, thetherapeutically effective dose can be estimated initially in vitro, forexample, from cell culture assays, as disclosed herein. For example, adose can be formulated in animal models to achieve a circulatingconcentration range that includes the EC50 (effective dose for 50%increase) as determined in cell culture. Such information can be used tomore accurately determine useful doses in humans.

It will be understood, however, that the specific dose level for anyparticular patient will depend upon a variety of factors including theactivity of the specific compound employed, the age, body weight,general health, sex, diet, time of administration, route ofadministration, and rate of excretion, drug combination, the severity ofthe particular disease undergoing therapy and the judgment of theprescribing physician.

For administration to non-human animals, the drug or a pharmaceuticalcomposition containing the drug may also be added to the animal feed ordrinking water. It will be convenient to formulate animal feed anddrinking water products with a predetermined dose of the drug so thatthe animal takes in an appropriate quantity of the drug along with itsdiet. It will also be convenient to add a premix containing the drug tothe feed or drinking water approximately immediately prior toconsumption by the animal.

Toxicity and therapeutic efficacy of such conjugates can be determinedby standard pharmaceutical procedures in cell cultures or experimentalanimals, e.g., for determining the LD50 (the dose lethal to 50% of thepopulation) and the ED50 (the dose therapeutically effective in 50% ofthe population). The dose ratio between toxic and therapeutic effects isthe therapeutic index and it can be expressed as the ratio between LD50and ED50. Conjugates that exhibit high therapeutic indices arepreferred. The data obtained from these cell culture assays and animalstudies can be used in formulating a range of dosage for use in humans.The dosage of such conjugates lies preferably within a range ofcirculating concentrations that include the ED50 with little or notoxicity. The dosage can vary within this range depending upon thedosage form employed and the route of administration utilized. The exactformulation, route of administration and dosage can be chosen by theindividual physician in view of the patient's condition. (See, e.g.Fingl et al., 1975, in “The Pharmacological Basis of Therapeutics”, Ch.1, p. 1).

In particularly preferred embodiments of the present invention areprovided conjugates comprising antibiotic, antibacterial, antimycotic,antiviral, antiproliferative or antineoplastic drugs for specificdelivery to or accumulation in specific organs, tissues and cells in ananimal. In particularly preferred embodiments, the conjugates aretargeted to the central nervous system, most preferably brain tissue,for the alleviation or amelioration of pathological disease statestherein. In such embodiments of the invention are provided methods andconjugates for facilitating the transit of such conjugates ofantibiotic, antibacterial, antimycotic, antiviral, antiproliferative orantineoplastic drugs, agents and conjugates across the blood-brainbarrier and into targeted regions of the brain and other physiologicallyprotected sites, for the treatment of animal, preferably human, diseasesand pathological conditions. Among the most common such diseases andconditions are acquired immune deficiency syndrome, neuroblastoma,glioma, astrocytoma, meningioma, sarcoma, metastatic melanoma,metastatic adenocarcinoma, lung tumors such as adenocarcinoma, smallcell carcinoma, and other tumors of the lung; tuberculosis; bronchitis;emphysema; pneumonia; cystic fibrosis; Gaucher's disease; and otherdiseases and disorders of lung or spleen tissue; syphilis, encephalitis,meningitis, nocardiosis, abscess, coccidiodomycosis, cryptococcosis,subdural empyema, extrapulmonary tuberculosis, leptospirosis,toxoplasmosis, trichinosis, trypanosomiasis, mycoplasma infection,herpetic encephalitis, and schistosomiasis.

Animals to be treated with the inventive conjugates using the methods ofthe invention are intended to include all vertebrate animals, preferablydomesticated animals, such as cattle, horses, goats, sheep, fowl, fish,household pets, and others, as well as wild animals, and most preferablyhumans.

The following Examples illustrate certain aspects of the above-describedmethod and advantageous results. The following examples are shown by wayof illustration and not by way of limitation.

EXAMPLE 1

Conjugates between melatonin and melatonin derivatives withbiologically-active compounds were prepared as follows.

As a first step, melatonin is converted to modifiable melatoninderivatives, illustrated herein by the indole N—OH and indole N-formoxyester derivatives.

Alternatively, serotonin is converted to demethoxylated melatonin(N-acetyl serotonin).

Levadopa conjugates as shown in FIG. 1 can be prepared from either ofthe indole N melatonin derivatives. In the following synthetic scheme,all hydroxyls and hydrazine protons of levadopa are protected byreaction with trimethyl silyl chloride to form TMS adducts. Theseadducts are removed after reaction by treatment in dilute acid.

or the ring hydroxylated product:

Synthesis of N-Hydroxy Melatonin

The synthesis of N-hydroxy melatonin uses conditions described byBilaski and Ganem (1983, Synthesis, p.537). Briefly, to a 100 mLround-bottomed flask is added 1 g (4.3 mmol) melatonin, 50 mL of 25%water in isopropyl alcohol, and 2.84 g (20 mmol) disodium hydrogenphosphate. The solution was cooled to 0° C. under argon, followed by theslow addition of 1.56 g (6.5 mmol) benzoyl peroxide over 4 hrs. Afterstirring at 0° C. for 20 hr the reaction was quenched by the addition of10 wt % sodium thiosulfite, followed by 5×50 mL washes with methylenechloride. The methylene chloride fractions were combined and solventremoved under reduced pressure. The product was recrystallized frombenzene/chloroform to yield 266 mg (1.07 mmol) of N-hydroxy melatonin.

Synthesis of N-Alkoxymethyl Melatonin

To a 100 mL round-bottomed flask is added 1 g (4.3 mmol) melatonin, 50mL of methylene chloride, and 2.02 g (20 mmol) diisopropyl amine. Thesolution was cooled to 0° C. under argon, followed by the slow additionof 0.64 g (4.3 mmol) of the chloromethyl ester of 3,3,3-chlorodimethylacrylate over 1 hr. (Chloromethyl ester of 3,3-dimethyl acrylate isprepared by an analogous procedure for the synthesis of benzylchloromethyl ester set forth in Organic Synthesis Col III: 101.) Afterstirring at 0° C. for 20 hr the reaction was quenched by the addition of10 mL of 4.0 M hydrochloric acid and 2×10 mL of brine, followed bydrying over anhydrous sodium sulfate. The solution was filtered,concentrated and purified by recrystallization from benzene to yield1.3g (3.8 mmol) of (N-methyl ester of 3,3-dimethyl acrylate) melatonin.

Synthesis of N-Acetyl Serotonin

N-acetyl serotonin was synthesized as follows. 100 mg (0.47 mmol)serotonin hydrochloride and 10 mL of pyridine were mixed in a 100 mLround-bottomed flask, and the solution was cooled to 0° C. under argon.Acetic anhydride (2.84 g, 28.4 mmol) was added slowly over 1 hr. Afterstirring at 0° C. for 20 hr the reaction was terminated by removing thevolatile reagents under high vacuum. The remaining syrup was dissolvedinto 25 mL of methylene chloride and washed with 0.1 M HCl until the pHof the aqueous phase was less than 3. The organic phase was dried underanhydrous sodium sulfate, filtered and concentrated to yield a syrup. Tothis syrup was added 25 mL of aqueous isopropyl alcohol (50 wt %) andthe solution was cooled to 0° C. Sodium hydroxide (1 mL of a 1.0 mMsolution) was added and stirred at 0° C. for 4 hr. The solution wasneutralized with acetic acid, concentrated and filtered through a shortplug of silica gel with ether, concentrated and recrystallized frombenzene/chloroform to yield 27 mg (0.11 mmol) of N-acetyl serotonin.

It should be understood that the foregoing disclosure emphasizes certainspecific embodiments of the invention and that all modifications oralternatives equivalent thereto are within the spirit and scope of theinvention as set forth in the appended claims.

1. A method for treating a pathological condition or disease state in cells, tissues or organs in a human or animal, the method comprising the step of administering to the animal a pharmaceutical composition comprising a psychotropic, neurotropic or neurological drug, or an antibiotic, antibacterial, antimycotic, antiviral, antiproliferative or antineoplastic drug, an amino acid or amino acid derivative specifically transported into a physiologically-protected site, two linker functional groups and a spacer, wherein the spacer has a first end and a second end and wherein the amino acid or amino acid derivative is attached to the first end of the spacer through a first linker functional group and the drug is attached to the second end of the spacer through a second linker functional group, in an acceptable carrier or formulation and in an amount sufficient to alleviate the pathological condition or disease state in the animal.
 2. A method of claim 1, wherein the pathological condition or disease state is present in a physiologically restricted or protected site in the human or animal.
 3. A method of claim 1, wherein the pharmaceutical composition comprises L-dopa, hydroxytryptamine, amantadine, benztropine, bromocryptine, diphenhydramine, levadopa, pergolid, trihexphenidyl, ethosuximide, valproic acid, carbamazepine, 10-hydroxycarbamazepine, 11-hydroxycarbamazepine, primidone, gabapentin, lamotrigine, felbamate, paramethadione, trimethadione, phenothiazine, thioxantheme, clozapine, haldoperidol, loxapine, a benzodiazapene antidepressants of the norepinephrine reuptake inhibitor type, a monoamine oxidase inhibitor, carotene, glutathione, N-acetylcysteine, methotrexate, azidothymidine, dideoxyinosine, dideoxycytosine, acyclovir, or gancyclovir.
 4. A method for treating a pathological condition or disease state in cells, tissues or organs in a human or animal, the method comprising administering to the animal a pharmaceutical composition comprising a psychotropic, neurotropic or neurological drug, or an antibiotic, antibacterial, antimycotic, antiviral, antiproliferative or antineoplastic drug, having a first functional linker group, and an amino acid or amino acid derivative specifically transported into a physiologically-protected site, having a second functional linker group, wherein the drug is covalently linked to the amino acid or amino acid derivative by a chemical bond between the first and second functional linker groups, in an acceptable carrier or formulation and in an amount sufficient to alleviate the pathological condition or disease state in the animal.
 5. A method of claim 4, wherein the pathological condition or disease state is present in a physiologically restricted or protected site in the human or animal.
 6. A method of claim 4, wherein the pharmaceutical composition comprises L-dopa, hydroxytryptamine, amantadine, benztropine, bromocryptine, diphenhydramine, levadopa, pergolid, trihexphenidyl, ethosuximide, valproic acid, carbamazepine, 10-hydroxycarbamazepine, 11-hydroxycarbamazepine, primidone, gabapentin, lamotrigine, felbamate, paramethadione, trimethadione, phenothiazine, thioxantheme, clozapine, haldoperidol, loxapine, a benzodiazapene antidepressants of the norepinephrine reuptake inhibitor type, a monoamine oxidase inhibitor, carotene, glutathione, N-acetylcysteine, methotrexate, azidothymidine, dideoxyinosine, dideoxycytosine, acyclovir, or gancyclovir.
 7. The method of claims 1 or 3, wherein the disease state is a neurological disease.
 8. The method according to claim 7 wherein the neurological disease is Alzheimer's disease, Parkinson's disease, epilepsy, seizure disorder, migraine or Lennox-Gastaut syndrome.
 9. The method of claims 1 or 3, wherein the disease state is a neuropathy.
 10. The method of claim 9 wherein the neuropathy is trigeminal neuralgia, diabetic neuropathy or shingles.
 11. The method of claims 1 or 3, wherein the disease state is a psychological disorder.
 12. The method of claim 11 wherein the psychological disorder is bipolar disorder, explosive aggression, depression or agitation associated with elderly dementia.
 13. The method of claims 1 or 3, wherein the disease state is a microbial infection.
 14. The method of claim 13, wherein the disease is AIDS, encephalitis, meningitis, or syphilis.
 15. The method of claims 1, 2, 3, 4, or 5, wherein the disease state is a malignant or benign tumor or proliferative disease.
 16. The method of claim 15, wherein the disease is neuroblastoma, glioblastoma or astrocytoma.
 17. The method of claims 1 or 3, wherein the disease state is present in testes.
 18. The method of claims 1 or 3, wherein the disease state is present in spleen.
 19. The method of claims 1 or 3, wherein the disease state is present in an eye.
 20. The method of claims 1 or 3, wherein the disease state is present in brain, central nervous system or other neurological tissue. 